Last updated September 22, 2026. Not a lab test. Hours below are arithmetic: published watt-hours ÷ a named heater watt figure. We did not run an enclosure overnight. This is not veterinary advice.
Size the battery from two numbers: the heater’s named watts, and the battery’s watt-hours.
Hours ≈ battery Wh ÷ heater watts.
That divide is a 100% duty-cycle ceiling, not a vivarium test. Heat is a sustained resistive load. A heat mat or ceramic heat emitter that stays on draws its nameplate watts for as long as it is powered. That is harder on a battery than a nebulizer treatment that runs a few minutes at a time. A thermostat can cycle the heater off once the set point is hit, so real average watts may be lower—but size from the nameplate first, then treat any cycling as unearned headroom.
AC power stations add inverter loss, so real AC hours are shorter than the raw divide. Desktop UPS units often switch fast but hold far fewer watt-hours than a portable power station. Pick the tool for the outage length you actually need.
Affiliate note: Off Grid Power Boom may earn a commission from qualifying purchases. The site header already carries the disclosure—this is the one body reminder for this draft.
Named heater watts (manufacturer pages)
Zoo Med ReptiTherm Under Tank Heaters
Zoo Med’s ReptiTherm U.T.H. page lists:
| Item | Size | Dimensions | Named watts | Gallon guide |
|---|---|---|---|---|
| RH-7 Mini | Mini | 4″ × 5″ | 4 W | 1–5 |
| RH-4 | Small | 6″ × 8″ | 8 W | 10–20 |
| RH-5 | Medium | 8″ × 12″ | 16 W | 30–40 |
| RH-6 | Large | 8″ × 18″ | 24 W | 50–60 |
Zoo Med’s Snake Strip U.T.H. (RH-11) is 10 W (3.5″ × 18″).
Exo Terra Heat Mats
Exo Terra’s NA operating instructions for PT2015–PT2018 list:
| SKU | Named watts | Size | Gallon guide |
|---|---|---|---|
| PT2015 | 4 W | 4″ × 5″ | 1–5 |
| PT2016 | 8 W | 8″ × 8″ | 10–20 |
| PT2017 | 16 W | 10″ × 11″ | 30–40 |
| PT2018 | 25 W | 11″ × 17″ | 50–60 |
Source PDF: Exo Terra Heat Mat NA instructions.
Exo Terra’s self-regulating PTC line (PT2031–PT2034) is listed as 4 W / 8 W / 16 W / 24 W on the Heat Mat 4W PTC product page and matching PTC instructions PDF.
Fluker’s Ceramic Heat Emitters
Fluker Farms’ Ceramic Heat Emitter page lists emitters available in 60 W, 100 W, and 150 W. Product schema text on that page repeats “Available in the following watts: 60, 100, 150.” Use a ceramic-socket fixture rated for the chosen wattage.
Zoo Med Repti Basking Spot Lamps
Zoo Med’s Repti Basking Spot Lamp page lists discrete bulbs including 25 W, 40 W, 50 W, 75 W, 100 W, 125 W, 150 W, and 250 W (item numbers SL-25 through SL-250). Basking bulbs are daytime radiant loads; many keepers still need a separate night heat path (UTH or CHE).
Thermostat load ceiling (not heater watts)
A thermostat does not replace the heater’s watts—it switches them. INKBIRD’s ITC-308 product page lists output power for the US ITC-308 as 120VAC 60Hz 10A / 1200W (total two receptacles) MAX. Do not hang a 150 W CHE plus other loads past that combined receptacle limit. Herp-specific proportional controllers have their own amp ratings—read the model you own.
Worked Wh ÷ W examples (arithmetic only)
Use two portable stations already cited on Boom’s CPAP sizing page:
- Jackery Explorer 300 Plus — 288 Wh, 300 W AC (model JE-300B)
- BLUETTI AC70 — 768 Wh, 1,000 W AC
Hours below = Wh ÷ named heater watts. Not a lab test. Inverter loss is ignored in the raw divide (real AC hours are shorter).
| Heater (named W) | Source | Hours on 288 Wh (arithmetic) | Hours on 768 Wh (arithmetic) |
|---|---|---|---|
| Zoo Med RH-7 Mini, 4 W | Zoo Med | 72.0 | 192.0 |
| Zoo Med RH-4, 8 W | Zoo Med | 36.0 | 96.0 |
| Zoo Med Snake Strip RH-11, 10 W | Zoo Med | 28.8 | 76.8 |
| Zoo Med RH-5, 16 W | Zoo Med | 18.0 | 48.0 |
| Zoo Med RH-6, 24 W | Zoo Med | 12.0 | 32.0 |
| Exo Terra PT2018, 25 W | Exo Terra PDF | 11.5 | 30.7 |
| Fluker’s CHE, 60 W | Fluker Farms | 4.8 | 12.8 |
| Fluker’s CHE / Zoo Med spot, 100 W | Fluker / Zoo Med | 2.9 | 7.7 |
| Fluker’s CHE, 150 W | Fluker Farms | 1.9 | 5.1 |
| Zoo Med Repti Basking Spot, 250 W | Zoo Med | 1.2 | 3.1 |
Read the table honestly: a small UTH can ride a 288 Wh station for more than a calendar day on paper. A 100–150 W ceramic emitter burns the same pack in a few hours. Continuous heat is not a nebulizer treatment cycle.
Energy needed for a target outage at continuous nameplate:
- 8 W mat × 12 hours = 96 Wh (before inverter loss)
- 24 W mat × 12 hours = 288 Wh
- 60 W CHE × 12 hours = 720 Wh
- 100 W CHE × 12 hours = 1,200 Wh
UPS vs portable power station
Desktop / rack UPS: Fast transfer (often under ~10 ms on line-interactive / online units). Typical consumer UPS batteries are sized for minutes of PC shutdown, not overnight heat. Fine as a bridge for a very short blip if the VA rating exceeds the heater watts—poor for multi-hour outages unless you verify published Wh (most UPS marketing quotes VA/minutes, not Wh).
Portable power station (PPS): Published Wh is usually on the box. Pure-sine AC outlets can feed the same wall-wart heat mat, CHE clamp lamp, or thermostat strip you already use. Many units offer UPS/EPS pass-through modes; transfer times vary by brand—read the maker page for the model you buy. Wh capacity is why a PPS usually wins for reptile heat: you need sustained watts for hours, not just a clean handoff.
Practical path for many keepers: keep the primary heat path (often the lowest-watt UTH behind a thermostat) on the station or UPS, and treat high-watt daytime basking bulbs as optional during an outage. That is a planning choice, not a health claim.
Soft station shortlist (makers’ Wh; Awin / maker links)
Confirm live maker stock before you buy. Soft Awin / maker links only—no Amazon shortcodes on this page.
Jackery Explorer 300 Plus — 288 Wh
Jackery US: 288 Wh, 300 W AC. Arithmetic at Zoo Med RH-4 8 W: 36.0 hours. At Fluker’s 60 W CHE: 4.8 hours. Short for multi-hour ceramic heat; workable for a small mat if that is truly the only critical load.
Check Jackery Explorer 300 Plus (Jackery US)
BLUETTI AC70 — 768 Wh
BLUETTI US: 768 Wh, 1,000 W AC. Arithmetic at 8 W: 96.0 hours. At 60 W: 12.8 hours. At 100 W: 7.7 hours. Better multi-hour CHE headroom on paper. Confirm kit vs bare station on the maker listing before you buy.
Need more Wh for a 100 W+ continuous CHE through a long outage? Step up the station class and re-run Wh ÷ W with the maker’s published capacity—do not invent Wh. See also Boom’s portable power stations hub.
Related Boom job pages
Same math pattern, different loads:
- How to size a battery for a nebulizer compressor — short AC treatment loads
- How to size a CPAP backup battery — overnight device sizing
- How to size a battery for a 12V fridge — compressor cycling honesty
- Transfer switch safety — if you ever hardwire home circuits (UL 1008 / listed gear only)
Guides hub: how-to.
Non-electric footnote (not the affiliate core)
UniHeat’s 40 Hour Heat Pack page describes a disposable shipping warmer rated for up to 40 hours once activated (air-activated; single-use). UniHeat FAQ guidance elsewhere stresses choosing duration for transit length and not placing warmers directly on or beside sensitive living things. Treat UniHeat as a shipping / short emergency insulation fallback discussion, not as a substitute for a sized electric heat path, and not as this page’s product shortlist. Follow the pack maker’s placement rules; Boom is not claiming enclosure outcomes.
What this page does not claim
- No “kept my snake / gecko alive” stories
- No overnight Boom lab tests
- No veterinary advice; ask a qualified herp vet for species temperature targets
- No invented watts—only named catalog figures above
Cited numbers (quick table)
| Product | Named watts | Source |
|---|---|---|
| Zoo Med ReptiTherm RH-7 / RH-4 / RH-5 / RH-6 | 4 / 8 / 16 / 24 W | zoomed.com |
| Zoo Med Snake Strip RH-11 | 10 W | zoomed.com |
| Exo Terra Heat Mat PT2015–PT2018 | 4 / 8 / 16 / 25 W | Exo Terra PDF |
| Exo Terra PTC Heat Mat PT2031–PT2034 | 4 / 8 / 16 / 24 W | exo-terra.com |
| Fluker’s Ceramic Heat Emitter | 60 / 100 / 150 W | flukerfarms.com |
| Zoo Med Repti Basking Spot | 25–250 W (listed SKUs) | zoomed.com |
| INKBIRD ITC-308 (controller ceiling) | 1200 W max total receptacles (US) | inkbird.com |
| Jackery Explorer 300 Plus | 288 Wh | jackery.com |
| BLUETTI AC70 | 768 Wh | bluettipower.com |
Sources
Re-fetched 21 September 2026 (PT); published 22 September 2026. No watt inventing.
- https://zoomed.com/reptitherm-under-tank-heater-u-t-h/
- https://zoomed.com/snake-strip-u-t-h-under-tank-heater/
- https://zoomed.com/repti-basking-spot-lamp/
- https://exo-terra.com/wp-content/uploads/PT2015_16_17_18_Heat_Mat_NA.pdf
- https://exo-terra.com/products/heating/substrate-heaters/heat-mat-4w-ptc/
- https://flukerfarms.com/ceramic-heat-emitter/
- https://www.inkbird.com/products/temperature-controller-itc-308
- https://www.jackery.com/products/jackery-explorer-300-plus-portable-power-station
- https://www.bluettipower.com/products/ac70
- https://uniheat.us/40-hour-heat-pack-uniheat/ (non-electric footnote only)
Robert DeWitt writes about off-grid power gear for Off Grid Power Boom. Based in Arizona, he uses portable power stations, solar panels, and battery systems regularly in extreme heat—focusing on practical runtime, charging speed, reliability, and real-world usability for camping, RV trips, and home backup.
Editorial focus: portable power stations & solar generators, solar panel setups, batteries/inverters, and off-grid preparedness.